The present invention relates to a high frequency relay for allowing or blocking high frequency signals to pass therethrough.
A conventional high frequency relay is disclosed in, for example, Japanese Patent Publication No. 7-23877. As shown in FIG. 16, this relay includes an electromagnet C having a coil A wound around an iron core B, stationary terminals D to be connected to the outside, contacts (movable contacts) E driven to move toward or away from the stationary terminals D, and a movable iron piece (armature) F to be attracted or repelled by the iron core B according to energization of the coil A that creates a driving force for driving the contact E.
As shown in FIG. 17, this high frequency relay has a mounting surface G to be mounted on a printed wiring board (outside) X. When this is mounted on the printed wiring board X, the stationary terminals D extend through the printed wiring board X and protrude beyond a rear surface thereof. The high frequency relay is fixed to the printed wiring board X by soldering the root of such protruding portion.
In the conventional high frequency relay referred to above, when it is mounted on the printed wiring board X, the stationary terminals D extend through the printed wiring board X and are fixed thereto so that the stationary terminals D, which constitute transmission paths for high frequency signals, protrude from the rear surface. It is, therefore, inevitably impossible to shield those portions that extend through or protrude from the printed wiring board X and, hence, the shielding properties with respect to the transmission paths for the high frequency signals are not so high.
The present invention has been developed to overcome the above-described disadvantages.
It is accordingly an objective of the present invention to provide a high frequency relay having high shielding properties with respect to the transmission paths for the high frequency signals and also having a simple structure with a reduced number of component parts.
In accomplishing the above objective, a high frequency relay according to the present invention has a mounting surface to be mounted on an external element and is characterized by including an electromagnet having an iron core and a coil wound around the iron core, stationary terminals to be connected to the external element, contacts formed to be generally flat and having respective contact surfaces to be brought into contact with or separated from the stationary terminals, an armature attracted to or repelled from the iron core according to energization of the coil to obtain a driving force for driving the contacts, and a pair of shielding members made of a metallic material for supporting the contacts in an insulated state so that the contact surfaces extend generally parallel to the mounting surface. The pair of shielding members shield contact portions between the contacts and the stationary terminals and sandwich the contacts in a direction perpendicular to the mounting surface.
Compared with the case where the contact portions of the stationary terminals with the contacts extend in a direction perpendicular to the mounting surface and the surfaces of the contacts similarly extend in the same direction, as shown in FIG. 16, the above-described construction can shorten the stationary terminals forming transmission paths for high frequency signals by a length corresponding to the width of the contacts at the contact surfaces, making it possible to enhance the shielding properties with respect to the transmission paths for the high frequency signals.
Furthermore, because the pair of shielding members are provided to sandwich the contacts in a direction perpendicular to the contact surfaces, i.e., in a direction perpendicular to the mounting surface, a plurality of contacts can be juxtaposed with one another over the mounting surface and, hence, the shielding members are not required for every pole and can be used for multi-pole relays. Accordingly, not only can the number of component parts be reduced but the high frequency relay can also be simplified in structure and reduced in size.
The high frequency relay according to the present invention is also characterized in that the stationary terminals have respective outer end portions substantially flush with the mounting surface and, hence, the stationary terminals can be used as the so-called SMD terminals to be soldered to an external surface. Accordingly, compared with conventional relays wherein the stationary terminals extend through a printed wiring board and protrude beyond a rear surface thereof, the stationary terminals forming the transmission paths for the high frequency signals can be shortened, making it possible to enhance the shielding properties with respect to the transmission paths for the high frequency signals.
The high frequency relay according to the present invention is also characterized in that the armature swings with a central portion thereof as a fulcrum when any one of opposite end portions thereof is attracted to or repelled from the iron core, wherein the armature has a first surface confronting the electromagnet and a second surface opposite to the first surface, and also has a drive member secured to the second surface thereof and having a longitudinal length shorter than that of the armature, and wherein a driving force from the armature is transmitted to the contacts via the drive member.
By this construction, the driving force obtained by the armature is transmitted to the positions inwardly of the opposite end portions of the armature via the drive member integrated with the armature. Accordingly, compared with the case where the driving force is transmitted to the positions in the proximity of the magnetic pole portions, the transmitting portions to which the driving force for driving the contacts is transmitted can be positioned close to the stationary terminals. As a result, the contacts can be brought into contact with or separated from the stationary terminals without enlarging the size of the contacts in a direction along the armature, making it possible to further enhance the shielding properties with respect to the transmission paths for the high frequency signals.
The high frequency relay according to the present invention further includes transit members having respective transmitting portions to which the driving force is transmitted. Because the transit members transmit the driving force to positions inwardly of the transmitting portions, the positions to which the driving force is transmitted can be brought closer to the fulcrum for the swinging motion. Accordingly, the length of the contacts can be further reduced and, hence, the shielding properties with respect to the transmission paths for the high frequency signals are high.
Furthermore, in the high frequency relay according to the present invention, the pair of shielding members are joined together by an electrically conductive adhesive. Accordingly, even if a gap is created between both the shielding members due to, for example, a dimensional tolerance, the electrical connection between both the shielding members is ensured, thus enhancing the reliability in shielding effects.
Also, in the high frequency relay according to the present invention, one of the pair of shielding members has insertion holes defined therein into which the contact support members are inserted, and the support members have metallic shielding portions at locations corresponding to the insertion holes. Accordingly, the reliability improves without lowering the shielding properties.
Moreover, because the support members have respective metallic support portions connected to one of the pair of shielding members, the contacts can be shielded at locations supporting the contact support members of an insulating material, enhancing the shielding properties.
Also, because the mounting surface is an external surface of one of the pair of shielding members, they can be grounded without providing any separate earth terminal, making it possible to reduce the number of the component parts and simplify the construction.
Furthermore, because distal ends of the stationary terminals are positioned inside the casing, the shielding effects can be further enhanced.
In addition, the high frequency relay according to the present invention further includes contact support members for supporting the contacts in an insulated state wherein the contact support members support the contacts in a direction substantially parallel to the mounting surface. Accordingly, in the case where the high frequency relay is used as a multi-pole relay, the contact support members are not required for every pole, making it possible to reduce the number of the component parts and simplify the construction.
The pair of shielding members are formed into a desired shape by metal-injection molding. Even if they have a complicated configuration, the metal-injection molding can readily process them and enables precise processing, resulting in a reduction in the size of the high frequency relay.
Also, because the pair of shielding members are joined together by laser welding, the joining can be ensured, providing sufficient shielding properties.
Furthermore, the high frequency relay according to the present invention is characterized in that the normally-closed stationary terminal, the coil terminal, the common stationary terminal, the coil terminal, the normally open stationary terminal, the normally open stationary terminal, the coil terminal, the common stationary terminal, the coil terminal, and the normally-closed stationary terminal are arranged around one of the pair of shielding members in this order.
This construction is advantageous when the high frequency relay is placed on a microstrip structure to constitute an attenuator circuit together with an attenuator element. More specifically, when the normally-closed stationary terminals directly connected to each other, the normally open stationary terminals connected via an attenuator element, and the common stationary terminals are provided by twos, they are arranged around one of the shielding members such that the common stationary terminals are led outwardly between the positions where the normally-closed stationary terminals and the normally open stationary terminals are led outwardly, and the coil terminals connected to the supply lines are led outwardly between the positions where the normally-closed stationary terminals and the common stationary terminals are led outwardly and between the positions where the normally open stationary terminals and the common stationary terminals are led outwardly. Accordingly, connecting lines for connecting the coil terminals and the supply lines do not cross any one of a connecting line for connecting the normally-closed stationary terminals and a connecting line for connecting the common stationary terminals, as viewed from above. Accordingly, the microstrip structure is not required to have any through-holes for a multi-level crossing among the connecting lines and, hence, sufficient impedance matching for the high frequency signals can be obtained.
Also, one of the pair of shielding members is formed into a rectangular configuration, and the normally-closed stationary terminals and the normally open stationary terminals are led out from one side and the opposite side of the one of the pair of shielding members, respectively. Accordingly, the normally-closed stationary terminals and the normally open stationary terminals can be separated, thus enhancing the isolation properties.
Moreover, if the one side and the opposite side are opposite short sides of the one of the pair of shielding members, the normally-closed stationary terminals and the normally open stationary terminals can be sufficiently separated, thus enhancing the isolation properties.